1. Field of the Invention
The applicant""s invention is a method and apparatus for use in orthognathic surgery. This type of surgery involves the correction of dentofacial deformities and is also referred to as maxillofacial surgery, reconstructive jaw surgery or surgical orthodontics.
During orthognathic surgery teeth and jaws of a patient are repositioned. Prior to surgery, desired changes to an original position of the patient""s teeth and jaws can be determined by clinical evaluation of the patient""s head, evaluation of the patient""s head X-ray, and evaluation of articulator mounted dental models. The desired changes to the teeth and jaws can be measured in three dimensions, parallel and perpendicular to reference planes. Three reference planes that can be used are a horizontal plane, a sagittal plane and a frontal plane. The horizontal plane is defined by three points on the patient""s head. The sagittal and frontal planes are perpendicular to each other as well as to the horizontal plane. The reference planes are common to the patient""s head, head X-ray and articulator mounted dental models. The desired changes to the teeth and jaws can be described in terms of x-, y-, and z-dimensions. The surgeon attempts to make actual changes to the original position of the teeth and jaws that are identical to the desired changes.
2. Description of Related Art
Prior art has been published by G. Wylie, B. Epker and J. Mosop in the International Journal of Adult Orthodontics and Orthognathic Surgery, 1988; 3:143-147. A technique is described to assist in designing osteotomies using a maxillary measuring appliance. The device consists of a horizontal table indexed to the teeth and having an adjustable calibrated vertical pillar that can slide along the length of the horizontal table. This technique is deficient in that orientation of the horizontal table is limited to a row of teeth as a reference line. Also, it is limited to one side of a dental arch at a time. Measuring as well as marking osteotomy lines is inaccurate due to parallax problems. Osteotomies cannot be designed in a continuous manner on both sides of a jaw. In addition, the device is limited to designing osteotomies and cannot measure and record an original position of or actual changes to teeth and jaws relative to reference planes.
A prior art method of measuring the actual changes to the teeth and jaws during surgery has been described by Erikson in Chapter 7 of the text titled Modern Practice in Orthognathic and Reconstructive Surgery, 1992, W. B. Saunders Company. He presents a technique whereby the surgeon uses calipers to obtain a vertical measurement prior to a maxillary osteotomy from a point on a cuspid tooth to a scribed mark on a maxilla superior to the osteotomy. A second measurement is made between the same two points after the jaw is repositioned in order to assess the actual changes.
Erikson""s technique is deficient in obtaining accurate measurements. It is difficult to measure the site with calipers due to parallax error. Measurements are limited to an intended y-dimension and exclude the x- and z-dimensions. The vertical measurement cannot predictably be made perpendicular to the same reference plane used prior to surgery to describe desired changes.
Other prior art was published by Perkins in the Journal of Oral and Maxillofacial Surgery, 1992; 50:1018-1019. He described an instrument manufactured and sold by Walter Lorenz Surgical, Inc of Jacksonville, Fla. It consists of a modified Boley gauge whose upper caliper is slipped onto a K-wire inserted into and extending from a skull in a nasofrontal region. A lower caliper has a wire extending from it that is approximated to a point of measurement on the teeth and jaws. Once measured, an original position of the teeth and jaws is changed by surgery and the same point is measured again. A difference in measurements indicates an actual change from the original position. Perkins"" method is deficient because it cannot predictably measure perpendicular to presurgical reference planes in x- and y-dimensions. Also, it cannot measure in a z-dimension.
Additional prior art was described by N. Stefanova and J. Stella in The International Journal of Adult Orthodontics and Orthopedic Surgery, 2000; 15:305-308. It involves using a large orthopedic caliper to make a measurement of an original position of teeth and jaws from an inferior medial canthus of an eye to a point on a tooth. A second measurement is made between the same points after the teeth and jaws are repositioned. The difference between the two measurements purportedly describes actual changes. This method is deficient in that it is difficult to reposition the caliper exactly the same way for each measurement. It cannot predictably measure relative to a presurgical reference plane in a y-dimension. Also, it cannot measure in x- or z-dimensions.
The applicant""s invention is a method and apparatus that assists a surgeon in making actual changes to teeth and jaws that are accurate with desired changes. The invention solves the problems inherent to prior art. It enables a surgeon at surgery to measure perpendicular and parallel to reference planes used prior to surgery to measure desired changes. Measurements can be made and described in x-, y-, and z-dimensions. The invention also enables the surgeon to measure and design osteotomies of a jaw that are accurately related to the presurgical reference planes in three dimensions.
The applicant""s invention is a method and apparatus that assists a surgeon in making actual changes to an original position of a patient""s teeth and jaws that are accurate with desired changes that were determined before surgery. The invention solves the problems inherent to prior art.
Using a known method prior to surgery, the patient""s dental models are mounted on an articulator, a known device, so that the models accurately reflect an orientation of the teeth and jaws to the patient""s jaw joints and to three reference planes of the patient""s head. The reference planes can be a horizontal plane, a sagittal plane and a frontal plane.
Also using known methods before surgery, desired changes to the teeth and jaws can be determined by evaluating the patient""s head, head x-ray and articulator mounted dental models. The desired changes to the teeth and jaws are measured relative to the chosen reference planes which are common to the patient""s head, head x-ray and articulator mounted dental models.
The invention assists the surgeon in accurate placement of the teeth and jaws by comparing the actual changes to the original position of the teeth and jaws with the desired changes to the teeth and jaws relative to the reference planes. This comparison is done by first recording the reference planes on a teeth indexing member prior to surgery. The recording of the reference planes is then transferred at surgery to the patient""s head by placing the teeth indexing member onto the patient""s teeth.
A port in a swivel member, which is fastened to the patient""s head with a cranial structure, is oriented to the reference planes by coupling it to the teeth indexing member with a coupling member. The swivel member is secured in place and the teeth indexing member is removed. The port in the swivel member now records the reference planes.
Using the coupling member, the oriented port of the swivel member is then coupled to a reference member which is positioned to a defined point on the teeth and jaws. The reference member indicates the original position of the teeth and jaws in any one of the x-, y-, or z-dimensions, or any combination of the x-, y-, and z-dimensions before the original position of the teeth and jaws are changed. The original position of the teeth and jaws in any one of the x-, y-, or z-dimensions, or any combination of the x-, y-, and z-dimensions is measured on the coupling member.
The reference member is adjusted to indicate the desired changes to the original position of the teeth and jaws. Surgery is then preformed which changes the original position of the teeth and jaws. The actual changes to the original position of the teeth and jaws in any one of the x-, y-, or z-dimensions, or combination of the x-, y-, and z-dimensions is compared with the desired changes to the original position of the teeth and jaws in any one of the x-, y-, or z-dimensions, or combination of the x-, y-, and z-dimensions. This is done by comparing the position of the adjusted reference member to the defined point on the teeth and jaws after the original position of the teeth and jaws is changed.
The invention provides a teeth indexing member with a horizontal slot and perpendicular scribe lines on its top surface. The teeth indexing member can be oriented to the articulator mounted dental models so that the horizontal slot parallels the horizontal reference plane and the scribe lines correspond to the sagittal and frontal reference planes. The teeth indexing member is indexed to the teeth of the patient""s articulator mounted dental models using an acrylic-like material.
The invention provides a swivel member with a rectangular port that is secured to the patient""s head with a cranial structure. The port of the swivel member is oriented to the horizontal slot and to the scribe lines of the teeth indexing member by inserting a rectangular horizontal rod of a coupling member. The port of the swivel member can be secured in place and thereby record the reference planes.
The invention provides a coupling member which consists of a calibrated rectangular horizontal rod which inserts into the rectangular port of the swivel member. A calibrated rectangular vertical rod is slidably supported perpendicular to the horizontal rod. A calibrated reference member is slidably supported perpendicular to the vertical member.
The invention also provides a method to assist in accurate placement of teeth and jaws of a patient during orthognathic surgery by designing desired osteotomies. Reference planes are recorded on a teeth indexing member prior to surgery. The teeth indexing member is positioned onto the patient""s teeth at surgery. An indicator member is used to design an osteotomy on a patient""s jaw. The osteotomy is compared with the reference plane.
The invention provides an indicator member that consists of a rod, which can be slidably engaged with a horizontal slot of a teeth indexing member, and a pointer that is slidably supported in a right angle manner by the rod. A tip of the pointer is directed in a nonparallel manner away from a perpendicular section of the pointer. Additional teeth indexing members can be oriented and indexed at various angles to the reference planes to permit the surgeon to accurately design and measure osteotomies at various angles to the reference planes.